Radial flow fan wheels are used widely in automotive heating, ventilation and air conditioning systems as well as in other systems where a relatively quiet movement of air is required.
Such fan wheels normally consist of a plurality of blades (for example thirty) depending from an annular member and extending parallel to a longitudinal axis of the fan wheel to define a substantially cylindrical envelope. Each blade is a thin elongated member having a cross-section defined by a pair of generally curved surfaces.
The blades are generally spaced apart regularly on a pitch circle, the spacing between the blades allows air which is input through the central part of the annulus to be expelled by the action of the blades and between the blades.
There are, however problems with known blower wheels in that the efficiency of the wheel is not optimised due to recirculation of air between the blades. The reduced efficiency is shown in the form of increased noise level from the blower, and as a result a higher input power is required to move the same volume of air.
Accordingly, it is an object of the present invention to at least partially mitigate the above-mentioned problems.